The present invention is directed to a device for aligning box blanks within a machine used for processing them, particularly for aligning blanks as they are being inserted into a folder-gluer.
Known folder-gluers are machines into which box blanks are fed one by one from underneath a pile in order to be carried into the various machine sections by means of conveyor belts for processing and to provide a "folded flat" and glued box blank at the end of the process in a terminal station. It is understood that the box blank undergoes several successive operations during its travel through the machine. Sequentially, the operations are effected as follows:
Pre-breaking of the first and third blank folds in the first section of the machine with a re-opening so as to transfer the blank in a flat condition into the second section; PA1 Applying glue in the station designed for this purpose and from where the blank is then carried to a third section; PA1 Folding the blank lengthwise on its second and fourth folds in the station designed for this purpose; PA1 Subsequently conveying the blank into a fifth section, wherein pressing and stripping occurs and discharging the folded and glued blank into a pile in a sixth section which is the discharge or delivery section for the folded and glued blank.
In order to obtain accurate folding along all folding lines, the box blanks must be carried through the machine without any hazard of sidewise or lengthwise skidding or sliding. To this aim, the machines are equipped with a combination of upper and lower conveyor belts, as well as, in certain cases, a combination of one or several lower belt conveyors with upper pressure roller tracks.
One of the major difficulties in folder-gluers is the lack of functional precision of the device occurring with the infeed devices for infeeding the blanks into the folder-gluer. These infeed devices generally consist of a lower conveyor with multiple belts operating, on the one hand, jointly with a front gauge and leaving between the gauge and conveyor belts just sufficient space for letting through one blank each time and, on the other hand, with a slide guide adjustable to the size of the blank to be fed in. The sequential infeed of the blanks can be achieved by means of an appliance acting in such a way as to partially and temporarily block or obstruct the space existing between the conveyor belts and the lower end of the front gauge to thereby prevent the departure of the lowermost blank from the blank pile situated in the infeed device. The force for moving each of the blanks out of the infeed device is explainable by the fact that the adherence or friction between the lower blank side and the conveyor belts is much higher and stronger than the rubbing or friction on the upper surface between the blanks of the pile.
However, on account of this very adherence and/or friction enhance rubbing, it might happen, in certain cases, that the blank does not benefit from an even driving force along its entire length. This uneven driving force can be caused by dirty belts so that the blanks are fed into the machine obliquely, thus, rendering subsequent folding along the desired folding lines of the blank very difficult.
Devices for the correcting of the inaccurate alignment of blanks have been devised and are, preferably, arranged in a section situated immediately after the infeed device. Attempts have been made to use them as a substitute for the first fold pre-breaking section. An alignment correction device well known in the trade consists of a straightener consisting of a row of staggered lower and upper rollers arranged on lower and upper beams which allow the distance from one another to be adjusted to the thickness of the blanks travelling therebetween. The device allowing the beams to be spaced one from the other includes, moreover, a device insuring permanent and variable pressure of the upper rollers onto the upper blank surface. Both the upper and lower beams are, moreover, to be conceived in such a way as to be arranged with the required and fixed angle with regard to the longitudinal axis of the machine.
The assembly thus conceived acts jointly with a lengthwise guiding rail. Hence, with the correct inclination imparted to the straightener, the action of the rollers of the straightener on one or the other surfaces of the blank will apply or urge the edge of the blank against the lengthwise guiding rail and insure the straightening of all blanks during the course of travel through the device. As a result of this straightening of the blanks, all blanks will be positioned so that their respective folding line will be perfectly parallel to the machine's longitudinal axis.
The rollers fitted on both the upper and lower beams are driven by a flat belt imparting its motion to the rollers by means of a pulley mounted on the axle of every roller of the upper and lower beams. The staggered arrangement of rollers, thus, allows vertical shifting of the upper beam so as to cope with the changes in the thickness of the blanks being processed without thereby squeezing the driving belts between the two pulleys, which would occur without the staggered arrangement.
The solution consisting in fitting the rollers of a straightener on upper and lower beams slanted with regard to the longitudinal machine axis involves the necessity to adjust the clearance of about 2 mm between the blank edge and the lengthwise guiding rail at an inlet of the straightening device so that at the outlet of the straightening device, the blank edge will be pressed against the lengthwise rail so that the folding lines and successive blanks will always be in the same position with regard to the downstream folding appliances. The result will be a kind of funnel effect which, in certain cases, presses the blank edges violently against the lengthwise guiding rail and, thereby, causes it to be damaged. On the other hand, the clearance set at the inlet of the straightening device between the blank edge and the lengthwise guiding rail requires accurate crosswise setting of the straightener with regard to the infeed of the device and, since this clearance may be variable, depending on the features of the blanks to be processed, the operator is to proceed manually to this setting excluding, thereby, any automatic lateral setting of the various machine appliances.
Another shortcoming of this type of straightener lies in the fact that the force exerted on the blank by the upper rollers is directed between the lower rollers, which are not vertically aligned with the upper roller, and may result in forming undulations in the blank in the event of excessive pressure necessitated by a very smooth and skidding blank, for instance blanks with the print on one side and watertight coatings on the other. These undulations of the blank, though slight, are sufficient for preventing straightening of the blank or else they will at least by likely to disturb the operation of the straightener. Moreover, this kind of straightener is to be withdrawn from the machine in the event of a processing of box blanks not allowing its use. This will result in a considerable loss of time for dismantling the machine and converting the section of the folder-gluer mentioned hereinabove.